1. Field of the Invention
Embodiments described herein relate generally to a method for fabricating a semiconductor device, a pattern writing apparatus, a recording medium recording a program, and a pattern transfer apparatus, and for example, relates to a method for fabricating a semiconductor device that controls a pattern formed on a mask and illumination light of a pattern writing apparatus that transfers the mask pattern onto a semiconductor substrate and related devices thereof.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor fabricating processes. In recent years, with an increase in integration density of an LSI, a circuit line width required for semiconductor devices is getting smaller year by year. In order to form a desired circuit pattern on such a semiconductor device, a high-precision original pattern (also called a reticle or a mask) is needed. In this case, an electron beam pattern writing technique essentially has an excellent resolution, and is used in production of high-precision original patterns.
FIG. 11 is a conceptual diagram for explaining an operation of a variable-shaped electron beam pattern writing apparatus. The variable-shaped electron beam (EB: Electron Beam) pattern writing apparatus operates as described below. In a first aperture plate 410, a quadrangular opening 411 to shape an electron beam 330 is formed. In a second aperture plate 420, a variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 of the first aperture plate 410 into a desired quadrangular shape is formed. The electron beam 330 irradiated from the charged particle source 430 and having passed through the opening 411 of the first aperture plate 410 is deflected by a deflector and passes through a portion of the variable-shaped opening 421 of the second aperture plate 420 to irradiate a target object 340 mounted on a stage continuously moving in one predetermined direction (for example, the X direction) with the electron beam 330. That is, a quadrangular shape which can pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 is formed in a pattern writing region of the target object 340 mounted on the stage continuously moving in the X direction. The scheme for causing a beam to pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 to form an arbitrary shape is called a variable-shaping scheme (VSB scheme).
With an increasing degree of integration of pattern, the line width precision of a pattern on a silicon wafer of up to 3 to 5 nm is now demanded. The method of changing illumination of a transfer apparatus (scanner) to increase the resolution of a pattern is proposed (see, for example, “Generation of arbitrary freeform source shapes using advanced illumination system in high-NA immersion scanners”, Proc. of SPIE Vol. 7640 764005-1). Also, the method of transfer by grouping patterns desired to be transferred onto a wafer and changing the shape of illumination light of each group by fitting to the trend of the pattern is proposed (see, for example, Japanese Patent Application laid-Open No. 2008-311502). However, dimensions change due to the optical proximity effect when a pattern of a mask is transferred onto a wafer and thus, the pattern is corrected to correct dimensional changes. Then, the corrected pattern will be formed on the mask. Thus, even if the illumination shape is selected by fitting to the pattern to be transferred, the actual mask pattern is different, causing dimension errors of the pattern. Further, dense patterns and coarse patterns are internally mixed in an LSI pattern. Thus, it is difficult to improve dimensional precision for all patterns at the same time.